Proliferation and frequency of cytokine-producing CD4⁺ T cells.

<p>Groups of young (6–8 weeks) and older (12 months) BALB/c mice were infected with 2×10⁶<i>L. major</i> promastigotes in one hind footpad. Four weeks post infection, the popiteal lymph nodes were harvested and restimulated with <i>L. major</i> parasites. The frequency of cytokine-expressing CD4⁺ T cells was determined by intracellular cytokine staining and the frequency of proliferating CD4⁺ T cells was determined by BrdU incorporation.</p><p>Data show the results of one representative experiment out of three independent experiments.